As I mentioned yesterday in the initial write-up, the inadvertently leaked “non-target” seats list is a peculiar mix.

For a start, it is far from complete – even if it were just a list of seats in which the Conservatives came nowhere near winning in 2010 there are plenty of safe Labour seats missing. Nor is it just limited to such constituencies – some are Tory-held with a variety of majorities, while others are numerically marginal seats for us to defend or attack.

Of course, it may be that this is just a clumsy use of words – perhaps someone in the web team just dumped a selection of pictures into a folder and casually labelled it “non target”. It’s also possible that the images were uploaded with their unfortunate title some time ago, and the situation has since changed (though if we assume they were all uploaded at the same time then there are some very recently selected candidates included).

All that said, I’ve had a go at crunching the numbers to see if we can wheedle out some rhyme or reason.

It’s a necessarily arbitrary exercise – I’ve made the cut off point between relatively safe and relatively marginal seats a majority of 4,000. Also, we must bear in mind that the prospects of a Lib Dem collapse and possible surges by the Greens, SNP and/or UKIP have the potential to produce results in 2015 which are drastically different from those we saw in 2010.

But even on this simple measure, it’s easy to see why 84 of the 102 seats might be viewed as “non-target”. Fourteen of them are held by the Conservatives with majorities above 4,000 votes – right up to Richmond, where William Hague won a 23,336 majority in 2010. Thirty-three are held by other parties with majorities above 4,000, too. And in a further 37 the non-Tory incumbents are not just over 4,000 votes ahead, but the Conservatives came in third or fourth in 2010.

So far, so uncontroversial. The remaining 18 constituencies are rather harder to explain.

Two – Dudley South and Cannock Chase – are Conservative-held seats with majorities of fewer than 4,000 votes. Both were also Conservative gains in 2010, and both of the first-term MPs are standing down this year. Both would, one would have thought, qualify for the defence half of the 40/40 – indeed, I’m told that they are part of that programme. And yet here they are. Their presence lends weight to the argument that the “non-target” label might be out of date or simply inaccurate.

Fifteen are, on paper at least, potentially fruitful attack seats – held as they are by Labour or the Lib Dems with majorities of fewer than 4,000 votes. In most of them, the majority is below 3,000, and in four – Birmingham Edgbaston, Plymouth Moor View, Eltham and Walsall South – it’s under 2,000. Would it really be sensible to class such seats as “non-target” when they are within reach if fortune provides an effective candidate, a good local campaign or a notably unpopular incumbent? It could of course be that the party has private reasons – such as the direction the Lib Dem vote swing – for thinking otherwise, but Cameron even touted Birmingham Edgbaston as a potential gain in the Autumn.

None of them appear in our best estimate of the list of 40/40 seats so in that sense they may not be formally included in the strategy, but it seems both unwise and insulting to attach a negative label to people with a good shot at getting elected. Perhaps it’s an accident – or perhaps it’s a symptom of the dismissive attitude of which various candidates have complained.

Then we come to the final seat labelled “non-target”: Rochester and Strood. For obvious reasons, this gained the most headlines – have the Conservatives given up on unseating Reckless? If this is a recent, accurate list which was given its label officially and intentionally, then that would appear to be the case. But given his low majority, it would be the height of foolishness not to have a good punt at taking back one of the two seats lost to UKIP defectors. Another point in the tally for this being the fruit of confusion rather than deliberate planning.

In conclusion, the list raises rather more questions than it answers. We should never rule out the possibility of a cock-up (or a series of cock-ups), particularly given the accidental way the story came to light. Nor do we have the full information – particularly the date at which the pictures started being uploaded, or the full criteria which led CCHQ to decide which seat would count as 40/40 and which would not. So while it ay well contain a kernel of truth, the picture is blurred by the high chance of other factors being at play.

Of course, this list’s very existence – and the manner in which it came out – suggest at best a troubling attitude towards candidates and a less than foolproof operation. That is worrying enough in itself.

Tory-held seats with majorities over 4,000

Richmond (Yorks) (23,336)

North East Hampshire (18,597)

Hertsmere (17,605)

Wealden (17,179)

Braintree (16,121)

Bexhill and Battle (12,880)

Boston and Skegness (12,426)

Havant (12,160)

Thirsk and Malton (11,281)

Bury St Edmunds (9,930)

South Suffolk (8,689)

South Cambridgeshire (7,838)

South East Cambridgeshire (5,946)

South Ribble (5,554)

Conservative seats with a majority below 4,000

Dudley South (3,856)

Cannock Chase (3,195)

Seats held by UKIP defectors

Rochester and Strood (2,920)

Labour or Lib Dem seats with a majority below 4,000

Birmingham Edgbaston (1,274)

Plymouth Moor View (1,588)

Eltham (1,663)

Walsall South (1,755)

Bridgend (2,263)

Luton South (2,329)

Wolverhampton North East (2,484)

Exeter (2,721)

Clwyd South (2,834)

Darlington (3,388)

Argyll and Bute (3,431)

Birmingham Selly Oak (3,482)

West Aberdeenshire and Kincardine (3,684)

Sefton Central (3,862)

Wrexham (3,658 over the Lib Dems, 3,768 over the Conservatives)

Seats held by other parties with a majority over 4,000 (or the Conservatives came below second place)